1. Field of the Invention
The invention relates to mechanism for converting predetermined alternating rotational movements to rectilinear movements and more particularly to combination locks utilizing a grooved cylindrical cam as the combination element.
2. The Prior Art
Many combination locks use tumblers as the combination setting means. A principal disadvantage of such locks is that when the dial of the lock is turned, there is a clicking noise when the various tumblers are moved which might be sufficient to enable an experienced person to determine the combination merely by turning the dial and listening.
Other combination locks have been proposed including grooved cylindrical cams alternately rotatable by setting a combination on a dial to unlatch the bolt which is manually retracted and manually projected into locking position at the same time recocking the combination mechanism cam and follower. Such an arrangement is disclosed in G. W. Hill U.S. Pat. No. 536,831. In G. C. Martin U.S. Pat. No. 915,199 the unlocking cam consists of a cylindrical member having groups of alternately reversing threads and a second threaded shaft, unidirectionally threaded, is provided for returning the mechanism to lock position. As in the Hill patent, M. A. Mosher U.S. Pat. No. 1,086,551 utilizes a lever type follower to release the bolt and the valve controlled by the bolt is manually rotated by a crank between its opened and closed positions. In E. M. Young Pat. No. 2,554,165 the combination mechanism comprises a group of stacked spaced discs with veins cut into their peripheries in opposite directions to permit the passage of the discs by some cam abutment, whereby the operating member acts on a portion of the bolt to retract it, projection of the bolt being effected by a spring when the operating member is rotated in the opposite direction.